1. Field of the Invention
The invention relates to a waste heat steam generator for hot, dust-loaded gases under overpressure with a gas inlet line, a gas outlet line as well as with heat exchanger elements through which a cooling medium flows.
2. Description of the Prior Art
Waste heat steam generators are known. They are used particularly in gas and steam turbine power generating stations. They serve to utilize the heat content of the hot gases of the gas turbine for generating additional live steam. They consist generally of a cylindrical or rectangular flue-like structure in which the hot waste gases flow from the bottom up successively through the heat exchanger tubes of the convection heating surfaces of the end superheaters, intermediate superheaters, evaporators and economizers.
Such waste heat steam generators are also utilized behind reduction plants and in chemical processes for the recuperation of heat. In waste heat steam geneators which are arranged after combustion installations it is also known to have the combustion gases flow from the top down into the waste heat boiler and for this purpose the heat exchanger heating surfaces are arranged in the reverse order (see Bennstoff-Warmekraft 35, 1983, No. 11, Pages 465 to 470 as well as No. 12, Pages 499 to 504).
In the heat recovery of the exhaust gases of pressurized coal gasification plants, additional problems arise in that high gas pressure as well as heavy dust loading and aggressivity of the gases must be added to the high gas temperature. Regarding the heat recovery in such plants, it is known to pre-cool the hot exhaust gases in a first pressure vessel equipped with heat exchanger heating surfaces, then to feed them into a following cyclone for dust removal and to cool them further in a second pressure vessel (British Patent Application No. 2,115,129=DE-OS 33 05 032).
British Pat. No. 653 540 discloses a heat exchanger in which the hot gas feeding line is arranged concentrically with the gas exhaust line. However, it is a peculiarity of this steam generator that it can be used only for dust-free gases because with dust laden gases, the lower spherical surface would become clogged up and the further flow of gas would be blocked.